autokinetic effect

The autokinetic effect refers to perceiving a stationary
point of light in the dark as moving. Psychologists attribute the perception
of movement where there is none to "small, involuntary movements of the
eyeball" (Schick and Vaughn 1995: 47).

The autokinetic effect can be enhanced by the power of
suggestion: If one person reports that a light is moving, others will be
more likely to report the same thing (Zusne and Jones).

Some, but not all, UFO sightings
are attributable to the autokinetic effect while perceiving bright stars or
planets such as Venus (Schick and Vaughn; Sofka).